This invention relates to a novel process for the preparation of 2,2'-bisphenol sulfoxides.
Generally, it is almost impossible to confine the oxidation reaction of aromatic sulfides solely to the formation of sulfoxides, and the problem is in that sulfones as by-products are incorporated in the reaction mixture. It has been recommended to use exclusively a particular oxidizing agent such as N-bromosuccinimides, bromine complexes of diazabicyclo[2,2,2]-octane, pyridine or quinolines, and the like in order to prepare solely sulfoxides at such a high selectivity that no sulfone is produced due to a side reaction.
Glacial acetic acid (peracetic acid oxidation) has been predominantly used as a solvent in the oxidation reaction of aromatic sulfides with hydrogen peroxide. However, it is difficult to prepare solely sulfoxides with selectively even with a theoretical amount of hydrogen peroxide used, because the sulfoxide itself is readily oxidized to form a sulfone.
That is, in many cases, the oxidation process of aromatic sulfides with hydrogen peroxide is essentially employed for the purpose of the preparation of the corresponding sulfones. The oxidation of known 2,2'-bisphenol sulfides with hydrogen peroxide is also effected in the presence of glacial acetic acid to obtain the corresponding 2,2'-bisphenol sulfones (J. Am. Chem. Soc., 67, 238 (1945)).